Drainage means for tank roofs



March 31, 1942. J. H. wlGGlNs 2,278,294

' DRAINAGE MEANS FOR TANK ROOFS Filedk March ll, 1940 www firman/6HL Patented Mar. 31, 1942 ANETED STATES PAT ortica 1 Claim.

This invention relates to large metal tanks of the kind that are used in oil elds to store petroleum products.

The object of my invention is to provide an oil storage tank whose component parts are combined in a novel manner that simplies and reduces the cost of the supporting structure for the roof of the tank, and also provides a reliable drainage means for the tank roof that is not afected by freezing weather. v

Briefly described, my improved tank is comf posed of ya vertical side wall, any suitable type or kind-of roof attached to said side wall, such, for' example, as a breather roof or balloon roof, a drain water collection chamber or receiving chamber arranged so as to receive drain water from the roof, and made of a ldiameter great enough to practically eliminate the possibility of water freezing in said chamber and bursting the same, and-an eductor leading from said co1- lection chamber and designed, constructed or arranged so that if, for any reason, the escape of water fromv said eductor is cut off or prevented, water will not freeze in said eductor and burst or disrupt same. The collection chamber or receiving chamber is arranged inside of the tank and attached to or combined with the tank in such a manner that the drain water in said chamber cannot come in contactwith or contaminate the material or substance conned in the tank.

that falls onto the tank roof to be discharged into or conducted to said collection chamber. The eductor, which is arranged inside of the tank, adjacent`the bottom of same-conducts drain water from the collection chamber to a sewer or to a point outside of the tank, and said eductor is of such construction and arrangement that there will always be an air space in said eductor, above the level of the water therein, irrespective of whether said eductor is functioning properly, or is in an inoperative condition. Said air space effectively prevents the eductor from lling with water to such an extent or degree as to cause the eductor to burst, in the event the Water therein freezes solid.

Figure l of the drawing is a transverse vertical sectional view of a liquid storage tank equipped with a roof drain constructed in accordance with my invention.

Figure 2 is a fragmentary sectional view, illustrating how said drain acts, in the event the out let of the eductor becomes clogged, or in the event the rate of discharge of waterfrom the eductor becomes materially less than the rate at .Any suitable means may be used to cause water which drain water enters the eductor from the collection chamber.

Figure 3 is a sectional view, taken on the line 3-3 of Figure 1.

Figure 4 is a fragmentary transverse vertical sectional view, illustrating another kind of eductor that may be used.

Figure 5 is a sectional view, taken on the'line 5 5 of Figure 4; and

Figure 6 is a perspective view of one of the partition plates used in the eductor shown in Figure 4. i

In the drawing A designates a large metal tank that is adapted to be used for storing liquid x, and B designates the top or roof of said tank. I have herein illustrated my invention in connection with a metal tank roof of the type or kind that is adapted .to iiex upwardly and downwardly so as to vary lthe volume o the vapor space of the tank, but'I wish it to be understood that my invention is applicable to rigid tank roofs., and in fact, to any type or kind of tank roof that employs a drain or drainage means, and which is used in a locality where 'freezing water is a problem that has to be reckoned with, in order to insure proper functioning and safe operation of the tank. The tank roof B herein shown is so shaped or formed that when it is in its normal downwardly flexed condition, Water that falls onto the top side of said roof will ow or drain to a discharge device or drain opening at the center of the roof, and when it is in its upwardly flexed condition, as shown in Figure 1, water thatfalls onto the top side of the roof will ow or drain outwardly towards the peripheral edge of the roof and escape from same. When the roof is in its normal downwardly deflected condition, it is substantially dish-shaped, and at such times the roof is supported by a supporting structure, usually formed from roof beams I that extend'radially from the center of the tank to the upper edge portion of the side wall of the tank.

My improved drain or drainage means comprises a receiving chamber or collection chamber C arranged inside of the tank and formed preferably by a 'vertically-disposed, tubular member 2 that extends upwardly from the center of the bottom 3 of the tank to a point above the level of the liquid in the tank, and an eductor D for conveying water out of said collection chamber, and discharging said water into a sewer F, or onto the ground at a point outside of the tank, said collection chamber and eductor being so constructed and combined with the tank that the water in said chamber and eductor cannot contannate or mix with the liquid :c confined in the tank.

While my broad idea contemplates the use simply of a drain hole in the tank roof, arranged so as to discharge drain water into the collectiony chamber C, I prefer to equip the roof with a burst-proof drain water discharge device of the liquid sealed type, such, for example, as a conventional inverted syphon drain, composed of a short, vertically-disposed pipe 4 that leads downwardly from a sump 5 at the center of the roof, and a relatively shallow cup or receptacle 6 attached to the lower end of said drain pipe 4 in such a way that the water in said cup will `seal the pipe 4, andthe Water that enters the receptacle 6 from the pipe 4 will overiiow the edge of said receptacle and drop downwardly into the collection chamber C. Owing to the fact that the cup or'receptacle 6 is relatively shallow, there is no danger of said receptacle being brokenor injured by water that freezes solid in said receptacle. The collection chamber C is of relatively great diameter, so as to tend to reduce the possibility of water freezing in said chamber and bursting the same, and in the form of my invention herein shown the chamber C is formed from a vertically-disposed metal cylinder 2, having its lower end connected by a welded jointrl to the bottom 3 of the tank, and made of' such height that it will serve as a supporting means for the ,roof beams I, whose outer ends are attached to the side wall of the tank. In order that my improved. drainage means will not cut down the storage capacity of the tank, I prefer to make the tubular member or cylinder 2 of the same height as the depth of the side wall proper of the tank, and attach an extension or collar 8 to the top edge of the tank side wall, so as to provide for thel downward ilexing of the roof and maintain the roof supporting beams I in an inclined position, sloping upwardly from the center of the tank.

The eductor D may consist of any suitable kind of conduit at the bottom of the tank that is either combined with the collection chamber C in such a manner, or which is of such construction, that it is impossible for said eductor to become completely filled with water, even though the escape or discharge of water Vfrom said eductor is cut oil. In the form of my invention shown in Figures 1 and 2 this result is attained by providing the eductor D with an inlet opening and a discharge opening located at a point f-ar enough below the top of the eductor, that it the escape or discharge of water from the eductor is lnterrupted, as for instance, due to the clogging of the outlet of the eductor, airwill collect in the upper portion of the eductor, and thus prevent the eductor from becoming completely filled with vwater entering same from the collection come completely filled with water, it is impossible for said eductor to burst or to be disrupted, due to water in same freezing solid. The eductor D shown in Figures 1 and 2, is formed from a metal plate bent into substantially inverted channel shape and connected by welded joints 9 to the bottom of the tank, thereby producing a recinlet I2 through which water is admitted to the eductor from thegcollection chamber C, and it is also provided with an outlet or discharge opening I3 through which water escapes from the eductor. As shown in the drawing, said inlet I2 and outlet I3' are located considerably below the `top or upper side of the eductor D. Usually, the

outlet or discharge of the eductor D will comprise a trap or inverted syphon I4- which co-acts with 6o chamber. Inasmuch as the eductor can never bel tangular-shaped conduit on the bottom of thel I of the tank. Said eductor D is provided with an 75,

the inverted syphon device on the roof of the tank to make the tank gas-tight, and if desired,

opening I2 at the lower end of said chamber into the eductor D, and thence'from the eductor into the sewer E or other point of discharge, through the discharge opening I3 of the eductor and the trap I4 that leads from said discharge opening. II the outlet of the eductor becomes clogged, water will continue to flow from the collection. chamber into the eductor until the water in the eductor rises high enough to submerge the openings I2 and I3 and trap air in the upper portion of the eductor that is used to create a force or pressure which effectively resists the escape of water from the collection chamber C into the eductor, and which eliminates the possibility oi the eductor D becoming completely filled with water. If, for any reason, water cannot get out of the eductor, then the highest possible level that water can rise in the eductor at atmospheric pressure, is the top of the inlet and discharge openings I2 and I3, the water in the collection chamber C continuing to rise. Under these conditions a pressure equal to a column of water the height of the tubular member 2 will be set up in the eductor D. The normal height of conventional oil storage tanks is about 40 ft., and consequently, a little over one atmospheric pressure will be 'set up in the eductor, and the air in the air space in the upper portion of the eductor, above the level of the water in the eductor, willbe compressed accordingly, but there will still be ample space left so that in the event the water in the eductor freezes solid, the ice can expand into the airspace in the upper portion of the eductor. The drain discharge device on the roof of the tankcan freeze solid, without liability of breaking, on account of the fact that the receptacle 6 of said device is made relatively shallow. When the apparatus is equipped with a trap or syphon I4 that forms part of the outlet from the eductor and which is usually buried in the ground, there is little liability of water freezingsolid in the-syphon I4, and causing it to burst. Consequently, my improved drainage means conducts drain water from the roof into a sewer, or to a point on the exterior of the tank, without danger 0f contaminating the liquid confined in the tank, and with little liability of the co-acting parts of the drainage means freezing solid and bursting in cold weather. In addition to having the desirable characteristics above mentioned; my improved tankV roof drainage means is inexpensive to construct, as it is lcomposed of a relatively few parts of simple design and rugged construction that can easily be tutes the collection chamber C is arranged at the'center of the tank, it can be used as a center support for the roof beams I, thereby reducing the cost and simplifying the construction of the supporting means for the tank roof.

In Figures 4. and 5 of the drawing I have i1- lustrated another form of eductor that may be used. Said eductor consists of a pipe or conduit B', of circular shape in cross section, mounted on the bottom of the tank between the tank side wall and the vertically-disposed, tubular member 2, and attached by welded joints or other suitable water-tight connections to said member and side wall, and provided intermediateits ends with a plurality of transversely-disposed partition plates I6 arranged in the upper portion of the eductor B'. The partition plates -I can be easily installed in or combined with the pipe that constitutes the eductor D' by sawing slots in the top side of said pipe, arrangingpartition plates I6 in said slots, and then securing said partition plates to the pipe by welded joints I1, as shown in Figure 4. Such an eductor can never be filled with drain water to such an extent that the eductor will burst when the water in same freezes solid, due of course, to the fact that when the water in the eductor rises above the bottom edges of the partition plates I6, a plurality of pockets or cushions of air become trapped in theupper portion of the eductor D'. n Said eductor can be sloped any reasonable amount, the degree of sloping of said eductor being determined by the spacing of the partition plates or separators I8.

Having thus 4described my invention, what I claim as new and desire to 'secure by Letters Patent is:

An oil storage tank provided at its center with i which drain water is discharged from the roof into said collection chamber under certain con-A said eductor.

JOHN H. WIGGINS. 

